Adjustable damping means for precision balance



A ril 7, 193 l A- 2,036,689

ADJUSTABLE DAMPING MEANS FOR PRECISION BALANCE Filed Dec. 50, 1933 6 Sheets-Sheet 1 zzz llllllll mum [IIIIIIII'III IIIIII INVENTOR JOHN GATTONI ATTORNEY April 7, 1936. J. GATTONH 2,035,689

ADJUSTABLE DAMPING MEANS FOR PRECISION BALANCE Filed Dec. 30, 1933 6 Sheets-Sheet 2 INVENTOR JOHN GATTONfl W ATTORNEY April 7, 19366 J. GATTQNH ADJUSTABLE DAMPING MEANS FOR PRECISION BALANCE v. Filed Dec. 50, 1933 6 Sheets-Sheet 3 INVENTOR JOHN GATTONI A ril 7, 1936. J. GATTONII 2036,689

ADJUSTABLE DAMPING MEANS FOR PRECISION BALANCE Filed Dec. 30, 1933 6 Sheets-Sheet 4 a I 93 T1 7 INVENTOR T -1' JOHN GATTONB ATTORN EY Aprifl 7 1936., J. GATTONH ADJUSTABLE DAMPING MEANS FOR PRECISION BALANCE Filed Dec. 50, 1933 6 Sheets-Sheet 5 Ti 1 E:

a INVENTOR JOHN GATTONfl ATTORNEY Aprfifl 7, 1936 .J. GATTQNH zpwfifigg I ADJUSTABLE DAD/[PING MEANS FOR PRECISI ON BALANCE Filed Dec. 30, 1953 6 Sheets-Shet 6 a .755 7% 7/7 71 m/sz m9 ma ATTORNEY Patented Apr. 7, 1936 ADJUSTABLE DAMPING MEANS FOR PRECISHGN BALANCE John Gattoni, Union City, N. J., assignor t Seeder-er-Kohlbusch, 1110., Jersey City, N. J., a corporation of New Jersey Application December 30, 1933, Serial No. 704,663

12 Claims.

This invention relates to magnetically damped precision balances of the type disclosed in my Patent $7 1,900,641, dated March '7, 1933, and has for its object to provide improved means for 5 controlling the damping effect in such balances.

The balance disclosed in Patent #1900541 has a pivoted beam supporting the scale pans, a magnet mounted below the beam, and a damping plate pivotally suspended from the beam in- 0 dependently of the scale pans and arranged to move up and down between the poles of the magnet. The eddy currents set up by moving the plate through the magnetic field dampen the motion of the beam and bring the balance to 15 rest in a few seconds whereas an undamped balance may take five minutes or longer to come to rest.

In the above balance the magnet may be adjusted with respect to the damping plate to vary the damping effect, this being desirable because the damping efiect may vary under different load conditions and also because some operators prefer to let the balance swing for a longer or shorter time than others. My balance has gone into such wide use in scientific laboratories, colleges, etc., and is used for such a wide variety of weighing operations, that it is increasingly desirable to simplify and expedite the adjustment of the damping unit under all conditions of use. The present invention accomplishes this and also provides an improved magnet-damper combination which increases the damping effect.

I shall describe several modifications of my invention, some of which may easily be applied to existing undamped balances. In all forms of the invention improved means are provided for supporting the magnet and for adjusting it toward and away from the damping plate to obtain any desired damping effect. Another important feature of the mounting is that the magnet may be rotated vertically and horizontally to bring its poles into proper alignment with the damping plate. The various adjustments are made independently in a minimum of time and without special skill on the part of the operator.

These and various other features and advantages of the invention will be described in connection with the accompanying drawings, in which:

Fig. 1 is a front elevation of a balance embodying the invention;

Fig. 2 is an end view thereof;

Fig. 3 is a horizontal section taken on line 3-3 of Fi 2;

Fig. 4' is a section taken'on line 4-4 of Fig. 3,

(Cl. 188l04) showing a detail of the adjustable magnet-supporting arm;

Fig. 5 is a vertical section taken on line 55 of Fig. 2, showing another detail of the magnetsupporting arm;

Fig. 6 is a plan View showing an alternative mounting of the magnet;

Fig. '7 is an end view showing a modified form of magnet and support;

Fig. 8 is a plan view of the assembly shown in Fig. 7;

Fig. 9 is a modified a top plan view of a balance having magnet adjusting mechanism;

Fig. 10 is a vertical section taken on line l0i 0 of Fig. 9;

Fig. 11 is of Fig. 9;

Fig. 12 is an end view looking into the left end a top plan view of a balance having another form of magnet adjusting mechanism; Fig. 13 is a vertical section taken on line l3l3 of Fig. 12;

Fig. 14 is of Fig. 12;

Fig. 15 is of Fig. 13;

Fig. 16 is an end View looking into the left end a detail section taken on line l5-I5 a front elevation of a balance having a modified damping plate suspension and magnet adjusting mechanism;

Fig. 17 is an end view looking into the right end of Fig.

Fig. 18 is a plan view of the magnet with the cooperating damping plate shown in section;

Fig. 19 is mechanism section;

a plan view of the magnet adjusting of Fig. 16 with parts of the frame in Fig. 20 is a horizontal section taken on line E B2D of Fig. 21;

Fig. 21 is of Fig. 19;

a vertical section taken on line 2 l--2 I Fig. 22 is a vertical section taken on line 2222 of Fig. 21;

knife edge knife edge bearing 2 pivotally supporting the 3 of beam i. The standard carries the usual bridge or cradle 5 which is adapted to support the beam so as to avoid damaging the knife edge also carries pivot when not in use. The beam the usual pointer B.

At the ends of the beam are knife edges 1 on which rest frames 9.

the knife edge bearings 8 of yoke These yoke frames carry upper and 33 in post 28.

lower hooks I and II which are pivoted thereto at I2 as best shown in Fig. 2. The scale pan bows I4 and I5 are hung on the upper hooks ID of the respective yoke frames.

A damping plate I6 of aluminum or other nonmagnetic material is freely suspended on the lower hook I I of the yoke frame at either or both ends of the balance. The balance illustrated in Fig. 1 has only one damping plate I6 and hence the hook II at the opposite end of the balance carries a small weight I1 which exactly balances this damping plate.

Cooperating with damping plate I6 and mounted horizontally below beam 4 is a circular magnet I8 which is constructed in the shape of a cylinder having a deep and narrow longitudinal slot forming closely spaced poles I9 as shown in Fig. 1. The damping plate moves up and down in the slot between these poles which provide a concentration of flux in its path.

The magnet supporting unit comprises two mating clamp members 2I22 which are held together around standard I by screw 23; a horizontal sleeve 24 which is secured to said clamp as hereinafter described; an extension rod 25 which is adjustable lengthwise in sleeve 24 and may be locked against rotation by screws 26 engaging a key-way 2'! in said rod; a post 28 which is swiveled in the enlarged end socket 29 of rod 25, being locked in adjusted position by screw 3! and having screw 32 at the top to prevent the post from dropping out of socket 29 when screw 3| is loosened; and a rod 33, carrying magnet i3, which is slidably mounted in post 28 and is locked in adjusted position therein by screw 34.

The connection between clamp 2I--22 and sleeve 24 is shown in Fig. 3. The sleeve abuts against clamp member 22 and has a reduced threaded shank 35 fitting loosely into recesses 36 and 37 which are formed in the adjacent sides of clamp members 2| and 22. Recess 31 is enlarged so as to form a shoulder for lock nut 38 which is threaded on shank 35 of sleeve 24. In this '-Way sleeve 24 may be rotated to the proper position with respect to clamp member 22 and secured thereto by lock nut 38. Clamp members ill and 22 are then secured to standard I by screw 23 and further by screw 39 which extends through clamp member 2! and screws into shank 35 of sleeve 24.

Thus the elbow joint comprising clamp 2 I22, sleeve 24, extension rod 25, swivel post 28 and slidable rod 33 may be adjusted quickly and accurately to move the magnet I8 either vertically or horizontally with respect to damping plate I6, or to rotate it Vertically or horizontally so as to align the poles It: with the damping plate. Vertical adjustment is effected by moving clamp El-22 on standard I, while horizontal adjustment parallel to beam 4 is effected by adjusting extension rod 25 in sleeve 25, and horizontal adjustment perpendicular to beam 4 or in the plane of damping plate I6 is effected by adjusting rod Rotation of magnet I8 in a vertical plane perpendicular to its own poles and to the damping plate I6 is accomplished by rotating rod 33 in post 28, while rotation of the magnet in a horizontal plane perpendicular to its poles and to the damping plate is accomplishedby rotating post 28 in socket 29 of rod. 25, this being the way to align the poles of the magnet with the damping plate. In all adjusted positions the magnet and support are clear of the bow I5 of the scale pan. After the magnet poles are properly aligned with the damping plate, the usual adjustment will be to move the magnet horizontally in the plane of the damping plate so as to get the plate symmetrically in the field when maximum damping efiect is wanted or asymmetrically of the field when less damping efiect is required.

In operation, the damping plate I6 moves in a vertical plane between the poles of the magnet I8 and the eddy currents set up by moving the plate through the field dampen the motion of the beam and quickly bring the balance to rest. The yoke frame 9 supports the damping plate I6 and the pan bow I5 independenly of and out of contact with each other so that swinging movements of the scale pan are isolated from the damping plate and cannot force the damping plate against the magnet poles which would seriously afiect the sensitivity and accuracy of the balance. In order to accomplish this, and at the same time produce exactly the right damping efiect, it is necessary to adjust the magnet carefully and accurately with respect to the damping plate and this is accomplished by my invention in a minimum time and without special skill on the part of the operator.

The magnet support shown in Fig. 6 is some what similar to that described above except that it has some of its parts rearranged so as to support the magnet with its flat sides parallel to the floor of the balance. extension rod 25 has an end socket 4| containing a horizontal aperture in which slidable rod 42 may be adjustably locked by screw 43. The other end of rod 42 has a socket 44 carrying a vertically slidable post which is fixed to the magnet. This post is locked in any desired vertical position by screw 45 and has a screw 46 at the top to prevent the post from dropping out of socket 44 when screw 45 is loosened. The post is not visible in the plan view of Fig. 6, being underneath socket 44, but it is similar to the post 28 of Fig. 5 except that its lower end is secured to the magnet. In this form of the invention the damping plate I6 moves up and down in a plane perpendicular to the fiat sides of the magnet and the damping effect may be varied by moving the magnet to the right or left as viewed in Fig. 6, movement to the left increasing the damping effect and movement to the right decreasing it.

Figs. 7 and 8 show a modification of the invention employing a horseshoe magnet 41 having closely spaced poles 48. This support is clamped to the standard I in the manner previously de scribed and has a sleeve 24 and adjustable extension rod 25 like the other supports. Rod 25, however, has an enlarged end socket 49 to which is fixed a stub rod 58 forming a right-angle elbow parallel to the floor of the balance. A socket 52 is slidably mounted on rod 58 and is secured in any adjusted position thereon by screw 53. The magnet is clamped between a pair of discs 54 and secured to socket 52 by bolt 55 and wing nut 56. The damping effect is varied by adjusting socket 52 along rod 50, a short rod being sufficient for this purpose since the magnet itself is long enough to reach the necessary distance between the legs of the pan bow I5. Other adjustments of the magnet are by rotary movement of sleeve 24, sliding movement of extension rod 25, and angular adjustment of the magnet between discs 54. All the foregoing magnet units may easily be applied to existing types of undamped balances.

In Figs. 9 to 11 the balance proper is similar to that previously described except that the bridge 5 has a rear extension 5! which forms a track In this construction the i for the backward and forward movement of a carriage 53 and has a stop block 59 to limit the movement of said carriage. The carriage has a rack 68, extension arms @l-62 parallel to the balance beam 2, and a brace 68 which supports and strength-ens said arms. Meshing with rack 69 is a pinion 95 mounted. on rotatable shaft 66 which extends outside the balance casing and is actuated by knob 6? for the purpose of adjusting the magnets.

The balance may be clamped at either or both ends of beam 4 and for purposes illustration I have shown damping plates to and cooperating magnets 18 at both ends of the beam. In this construction I use special yoke frames 68 having knife edge bearings 89 which rest on knife edges '5 at the ends of the beam, and having arms 19 which extend rearwardly of the beam. The damping plates iii are pivotally suspended from arms l9 as by rings 1 l, and these arms and plates are counterbalanced by weights "i2 which extend outwardly from the forward edges of the yoke frames. The scale pans are suspended from the yoke frames by means of hooks "it shown in Fig. 11. The magnets 59 are secured to horizontal rods l5 which are adjustably mounted in sockets it, these sockets being carried by vertical rods 7? which are suspended from the ends of ext nsion arms 6lfi2 by means of nuts 18. The magnets 18 are initially adjusted by rotating horizontal rods l5 as required by sliding them forward or backward in the planes of the damping plates and locking them in adjusted position by means of screws 79; also by rotating vertical rods ll to the desired position before tightening the nuts 18; and further by adjusting extension arms iii-52 to the right'or left as viewed in Figs. 9 and 10, and locking them in adjusted position by tightening screws 89 which fasten them to carriage 58 and brace 63. Thereafter, the damping effect may be varied quickly and accurately by turning knob 6'! of shaft 66, thereby moving carriage 58, extension arms 6|-62 and magnets 53 in a hori zontal direction with the magnets moving forward or backward in the planes of damping plates 86 or between right and left as viewed in Fig. ll.

In Figs. 12 to 15 the yoke frames 58 are constructed and mounted as in Figs. 9 to 11 except that the damping plates iii are suspended from arms 10 by means of light chains 32. The bridge 5 has a rear extension 83 supporting arm 83 which extends parallel to beam 4. Arm 84 has upturned ends 85 forming bearings for rotatable shaft 86 which extends outside the balance casing and is actuated by knob 83 for the purpose of adjusting the magnets. A leaf spring 88 is sprung between arm 8 and shaft 86 to hold the shaft in any adjusted position. Shaft 3E carries cam 89 which cooperates with arm S l to limit rotation of the shaft. In the form illustrated, I use horseshoe magnets 5? similar to that shown in Figs. '7 and 8 but circular magnets may be employed if desired. The magnets are clamped between discs 5&- and fastened to posts 9! by screws 92, these posts being adjustably mounted on stub rods 93 carried by shaft 8% and being secured to said rods by screws After the magnets are initially adjusted to align the poles with the damping plates, the damping effect is varied by turning knob 81 and thereby canting the magnets in a vertical plane as illustrated in dotted lines in Fig. 14.

The balance shown in Figs. 16 and 24 has another type of damping plate, suspension and control mechanism. The yoke frame 96 at one end of the beam has a bearing 9'! which rests on knife edge 1 as previously described, and carries a rod 93 which extends beyond both edges of the yoke frame. This rod has one end threaded at 99 for attachment of the damping plate and the opposite end weighted at ltd to counterbalance the damping plate. The yoke frame carries the usual suspension hook or hooks for bow l5 of the scale pan. The damping unit comprises damping plate l9! and two U-shaped members I92, all made of aluminum or other non-magnetic material, which are riveted or otherwise secured together at M33 with plate it'll in the middle forming a box-like structure with open ends adapted to receive the poles of the magnet. The upper edge of plate till has hooks m5 for engagement with light chains we hung from a strap If)? which is adjustably screwed to the threaded end 99 of rod 98 in a plane perpendicular to yoke frame 96. Hence damping plate lei is suspended in a plane parallel to beam l instead of being at right angles to the beam as in the balances previously described. The closely spaced poles of the magnet 598 extend inside the box-like damping unit on opposite sides of damping plate Ill! which cuts through the concentrated portion of the magnetic field while the side shields I92 cut the outer lines of force and thereby increase the damping effect. Thus the poles of the magnet lie parallel to plates fol, m2 and to balance beam 5 and must be adjustable lengthwise of said beam in order to vary the damping effect. This adjustable mounting of the magnet will now be described.

The magnet 5% is a horseshoe magnet and is clamped between die "39 by bolt H8 and wing nut 5 l2. The adju g mechanism is contained in a housing Hi3 having end plates H9 and H5 and a top plate l 85 containing a longitudinal slot Hi. This housing is adjustably mounted on a bracket H8 which is secured to the top of standard it; bracket i 23 extending through an opening in the front wall of housing i it and being secured by screws its to a plate i253 which spans the slot ill in top plate We of the housing as shown in Figs. 19 to 23. adjusted longitudinally, or between the left and right as viewed in Figs. l6, 19, 20, and 21, after which screws l l9 are tightened to hold the housing in the adjusted position.

Housing M3 contains a movable carriage comprising a vertical plate 522 and an angular strap 523 having a depending portion which extends through the open bottom of the housing and is secured to magnet by screws 12:3. The car riage runs on a double track composed of a hori- 1 zontal flange l' carried by the rear wall of housing l l3 and a horizontal rod @255 which is secured to the end plates H4 and N5 of the housing. A notch i2? is formed in the edge of carriage plate i222 as shown in Fig. 22, and a similar notch IE8 is formed in the depending portion of strap 523 as shown in Fig. 23, to allow the carriage to ride clear of track flange 525; and an adjustable screw 529, dep nding from "the horizontal portion of strap i23, rides on track flange N5 and therefore constitutes the sole point of engagement between the carriage and said flange 525 as shown in Figs. 21 to 23. Screw 529, when adjusted, causes magnet i 98 to rotate slightly in a vertical plane, making it possible to maintain the poles of the magnet in perfect vertical alignment with the damping plate.

The carriage plate has a central opening l3l for the passage of a rotatable spiral cylinder 32 which is journaled in the end plate H4 of In this way the housing may be housing H3 and is actuated by control rod I33 extending outside the balance casing and having an operating knob 34. The carriage plate I22 is provided on its under side with a screw I35 which extends into the spiral groove of cylinder I32 as shown in Figs. 21 and 22 whereby the rotation of cylinder E52, caused by turning knob E34 propels the carriage and magnet tilt either to the right or left in Figs. 19 to 21 according to the direction in which the knob is turned. Movement to the right is limited by screw i555 which extends through end plate I it? of housing i3 and may be adjusted as desired; while movement to the left is limited by contact et/Ween the end of spiral cylinder and the depending portion of carriage strap 523 as indicated in Figs. 2% and 21.

A pointer 38 is secured to carriage plate in, extending through the bottom of l li sing i3 and moving over a scale I38 on the front of the housing. This enables the position of magnet H58, and hence the damping eiiect, to be determined instantly and accurately according to the position of the pointer.

he invention is capable of various other modifications and adaptations not specifically described but eluded within the sc pe of the appended claims.

The invention claimed is:

l. A magnet unit for in ances con" ising a suppo ably clamping said supp to an ght, an extensible arm carried by so a magnet having closely spaced poles for c op ration with a vertically movable dam cally and horizontally rotv said magnet to said gning the poles of said magnet with said dampi. plate.

2. A magnet unit for magnetically damped balances comprising a supp ans i'or adjustably clamping said support to an upr'ght, a sleeve carried by said support, an extensi le ro adjustable in said sleeve, a magnet havl closely. spaced poles for cooperation with a ve ally movable damping plate, and a verticall a horizontally rotatable joint connecting said in cally damped balior adjustto said rod for aligning the poles of said magnet with said damping plate.

3. In a balance, a pivoted a magnet havelow said beam, a damping plate freely suspen 1 Il'Olll said beam and adapted to move in a vertical plane bev son the poles of said magnet to dampen the motion of said beam, and means for rotating said in a Vertical plane perpendicular to damping plate to align said poles with s2,

ing closely spaced poles mounted ing closely spaced poles mounted below a damping plate freely suspended from said beam and adapted to move a vertical plane between the poles of said magnet to dampen the motion i s for rotating said magnet in. vertical ontal plan perpendi ular to said darn g plate to 1 said pol with said damping plate.

5. In a balance, pivoted beam, a magnet ha ing closely spaced poles mounted belcv. a damping plate freely suspended from said and adapted to move in a vertical plane between the poles of said magnet to dampen the motion of said beam, means for rotating said magnet in a vertical plane pe pendicular to said damping plate to align said poles with said damping plate and means for moving said horizontally to vary the damping ci fect.

n" CD 6. In a balance, a pivoted beam, a magnet having closely spaced poles mounted below said beam, a damping plate freely suspended from said beam and adapted to move in a vertical plane between the poles of said magnet to dampen the motion of said beam, means for rotating said magnet in vertical and horizontal planes perpendicular to said damping plate to alien said poles with said damping plate, and means for moving said magnet ho 'izontally to vary the damping effect.

7. In a balance, a pivoted beam, a vertical damping plate freely suspended from said beam, a magnet having closely spaced poles adapted to lie on pposite sides of said damping plate to dampen he motion of said beam, a carriage supporting said magnet and adapted to be moved toward and away from said damping plate to vary the damping effect, and mea s for adjusting said magnet to align said poles with said damping plate,

8. In a balance, a pivoted beam, a vertical damping plate freely suspended from said beam, a magnet having closely spaced poles adapted to lie on opposite sides of said damping plate to dampen the mot-i n of said beam, a carriage supporting said magnet and adapted to be moved toward and away from said damping plate to vary the damping effect, a track for said carriage and means for adjusting said carriage on said track in a direction to align the poles of said magnet with said damping plate.

9. In a balance, a pivoted beam, a vertical damping plate freely suspended from said beam, a magnet having closely spaced poles adapted to lie on opposite of said damping plate to dampen the motion of said beam, a carriage supp ting said and adapted to be moved toward and away n said damping plate to vary the damping eff et, a track for said carriage, means for adju ng said car iage vertically on said track to align the poles of said magnet with said damping plate. and means for rotating said magnet horizontally on said carriage.

10. In a balance. a pivoted beam, a vertical damping plate I" ended from. said beam, a magnet having closely paced poles adapted to lie on opposite sides damping plate to dampen the motion of said beam, a carriage supporting said magnet and adapted to be moved toward and away from said damping plate to vary the damping effect, a track for said carriage, means for adjusting said carriage on said track a direction to align the poles of said magnet with said damping plate, a rotatable shaft and means actuated by said shaft for moving said carriage on said track.

11. In a balance,

pivoted beam a magnet having closely pcles mounted below and parallel to said I: Means for moving said gnet longitudina ly of said beam. and an openended boxlike unit freely suspended from said beam d aving vertical sides and a central vertical partition parallel to said beam and adapted to enclose the poles of said magnet to dampen the motion of said beam.

12. A damping unit for magnetically damped balances comprising iour-sided boxlike structure composed of hotl -magnetic material, having its ends open to recei' a the poles of a horsesnoe magnet having a central p rtition extending between to lie between said poles, for suspendin said damping unit from J OHN' GA'I'I'ONI. 

